Fluid control valves are often utilized in precisely controlling the amount of fluid applied to a system in response to valve controllers and actuators. The precise control of fluid is desired in such systems to control the delivery of a precise amount of fluid, or in order to conserve the application and use of fluid additives which may be extremely dangerous or highly expensive. The control valve also must provide a reliable sealing shut-off of the fluid flow when the valve is placed in the shut-off position to prevent the undesired loss of fluid through leakage. Often times a noise attenuator must be used in the pipeline system of either single stage or multi-stage attenuation capability so as to reduce the aerodynamic and hydrodynamic noise within the system, and it is desirable to include the noise attenuator within the fluid control valve.
Typically, such fluid control valves utilize a rotating ball control member mounted in a valve body passageway and with suitable sealing provided between the ball and the valve body. Normally, in a shut-off position of the ball control member the ball blocks the flow of fluid through the valve body passageway from an inlet to an outlet by virtue of the ball sealingly engaging a sealing member. The fluid flow is thus stopped by the ball control member and the reliable seal prevents the fluid from otherwise passing between the rotating ball control member and the valve body and undesirably leaking into the valve outlet.
In a typical fluid control member, the ball control member is rotated to the open position in the valve body passageway to enable fluid flow to pass from the valve inlet through the ball and to the valve outlet. However, in providing sufficient loading of the seal against the ball to assure a reliable seal during valve shut-off, this condition leads to a high degree of friction between the ball and the seal during ball rotation for controlling fluid flow. Thus, the high degree of friction resulting from the loading required to obtain a reliable seal during valve shut-off significantly impairs the ability to precisely position the ball control member which in turn determines the exact fluid flow which is desired in many instances. An added problem is the need to provide a noise attenuator mounted within the fluid control valve structure.
It is therefore desired to provide a fluid control valve including a noise attenuator and where there is provided a reliable valve shut-off seal condition. Furthermore, it is desired to provide such a fluid control valve and attenuator combination which can provide a much lower friction between the ball and the seal during valve operation so that precise control of the fluid flow can be obtained.